The River Gwash, a tributary of the River Welland, flows through the English counties of Leicestershire, Rutland and Lincolnshire. It rises just outside the village of Knossington in Leicestershire, near the western edge of Rutland. It is about 20 miles (32 km) long.
East of Stamford, its course is now fixed but it lies in a small flood plain which shows clear signs of the river's former meandering. The pasture fields include depressions which fill in wet seasons forming oxbow lakes, though they are not of the classical shape. Near Stamford it is the parish boundary between Stamford and Uffington.
Fish species 
The river supports a wild variety of fish species, including grayling and trout. Chub and dace inhabit the lower length below Newstead bridge in Stamford.
- Wheeler and Batty (1896), p.291
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